什么是同位素效应？相同条件下，下列哪个反应的速率更大？
(1)C2H3OH→C2H4+H2O；
(2)C2D5OD→C2D4+D2O。
下列会计职业道德规范中，要求会计人员树立服务意识，提高服务质量，努力维护和提升会计职业的良好社会形象的是()。
A. 爱岗敬业
B. 客观公正
C. 提高技能
D. 强化服务
同一主族氢化物的熔沸点随分子量的增大而升高，因此按沸点高低排序：H2O＜H2S＜H2Se。( )
？？Some people believe that using a DNA fingerprint may not be so reliable because？？
A. the accuracy of DNA fingerprinting has been challenged
B. no private laboratory foIloWs uniform. testing standards or quality controls
C. mistakes are possible when researchers explain the results of their tests
D. suspects may not have enough money to provide their own DNA to law-courts
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